Protein adhesive compositions

ABSTRACT

An adhesive composition having particular utility for the manufacture of laminated cellulosic products wherein one component is an aqueous alkali-dispersed protein and the other component is an oxazolidine, e.g. (5-hydroxymethyl-1-aza-3,7dioxabicyclo(3,3,0)octane).

United States Patent Stephanet al. [451 Dec. 19, 1972 [54] PROTEIN ADHESIVE COMPOSITIONS [56] References Cited [72] Inventors: John T. Stephan, Longview; A. J. UNITED STATES PATENTS Golick, Seattle, both of Wash. 7

1,950,651 3/1934 Behnke ..156/336 1 Assignw Commercial Solvents Corporation, 1, 16,436 10/1934 Cone ..l56/3 3.6 x New o u y 2,044,466 6/1936 Cleveland et al. .'.....156/336 x 22] Fiied: J 1 1971 2,291,586 7/1942 Galber et al ..l56/336 3,436,300 4/1969 Bryner ..156/336 X [21] Appl. No.: 107,434

Related s Appncation Data Primary Examiner-Harold Ansher Attorney-Howard E. Post et al. [62] Division of Ser. No. 815,197, April 10, 1969, Pat. 4 I

[57] ABSTRACT [52] 6 156/310 156/317 An adhesive composition having particular utility for I t C B32, 21/00 B3 6 the manufacture of laminated cellulosic products n k I [58] Field of Search ml/270, 156/336, 328, wherein one component 1s an aqueous al a 1 dispersed protein and the other component is an oxazolidine, e.g. (S-hydroxymethyl-l-aza-3,7-dioxabicyclo[3,3,0] octane).

1 Claim, N0 Drawings PROTEIN ADHESIVE COMPOSITIONS CROSS REFERENCE TO RELATED APPLICATIONS This application is a division of application Ser. No. 815,197, filed Apr. 10, 1969, now US. Pat. No.

BACKGROUND OF THE INVENTION This invention relates to protein adhesive compositions. In a particular aspect it relates to alkali-dispersed protein-oxazolidine combinations for the manufacture of laminated cellulosic products.

The use of adhesives to prepare laminated cellulosic products, e.g., plywood or paper products, is an old, well-known process and many different adhesives have been suggested. Presently, alkaline-dispersed protein adhesives and low temperature-curing phenoland resorcinol-formaldehyde resins are in widespread use.

' Soybeanprotein in an aqueous, alkaline dispersion, has long been in use as an adhesive for the manufacture of plywood, but it does not have the water resistance that has characterized the more recently employed hot press phenol-formaldehyde resin adhesives. Blood proteinis in widespread use, but supplies are limited and it is comparatively high priced. Blood has the advantage over soybean'protein in that its aqueous solutions are inherently thermosetting at temperatures above about 160 F. Thisenables the formulation of alkaline aqueous adhesive solutions which gel upon the application of heat. Such adhesives cure rapidly at elevated temperatures and have excellent water resistance. On the contrary, casein or soybean protein is thermoplastic and alkaline aqueous adhesives based on these materials set by a simple drying out procedure and/or chemical reaction. Such solutions do not ordinarily gel on one application of heat.

A need therefore exists for upgrading soybean and casein-based protein adhesives to perform a thermosetting function comparable with blood protein or thermosetting synthetic resin adhesives.

SUMMARY OF THE INVENTION It is an object of this invention to provide an improved process for laminating cellulosic articles.

Another object of this invention is to provide adhesives having a satisfactory working life.

Other objects will be apparent to those skilled in the art from the disclosure herein.

It has been discovered that an adhesive composition comprising a combination of an alkaline-dispersed protein and an oxazolidine represented by the formula:

- icyclo[3,3,0]octane, which hereinafter will be referred to as oxazolidine T.

DETAILED DISCUSSION The proportion of protein to oxazolidine in the composition of the present invention is not critical. Preferably, however, they are present in a ratio of about 3 to about 20 parts of protein (dry basis) to 1 part by weight of oxazolidine. Generally ahigh proportion of protein leads to longer working time. The bicyclic oxazolidines used in the adhesives of the present invention may be prepared according to the method of Murray Senkus, J. M. Chem. Soc. 67, 1515-1519(945) or that of William B. Johnston, U. S. Pat. No. 2,448,890. Generally these compounds are made by the reaction of 2 moles of formaldehyde with 1 mole of 2-amino-2-hydroxymethyl-l ,3-propanediol (T), or 2-amino-2-ethyl-1,3-propanediol (E). Other oxazolidines are known in the art but generally they are less satisfactory than the oxazolidines of the present invention.

The protein employed in the practice of this invention can be any of the proteins known to those skilled in the art. Generally, however, blood protein, although otherwise suitable, is satisfactory for use without the oxazolidines of the present invention. Other commonly used proteins suitable for the practice of the invention include, but are not limited to casein and soybean protein. The alkaline material and the amount used to effect protein dispersions is known in the art and the prior art practice'is suitable for the practice of this invention. As is generally recognized, a high proportion of alkaline material with respect to the protein can have a degradation effect which can render the protein non-gelling and ineffective as an adhesive. Ac-

cordingly, only sufficient alkaline material to effect the protein dispersion should be employed, as is known in the art.

The adhesive combination of this invention is especially suitable for use in manufacturing laminated cellulosic articles, such as laminated timbers, plywood and paper articles, particularly by the separate application process described in US. Pat. No. 2,015,806. In this process one component is applied to one surface and the second component is applied to the other surface. The two surfaces are joined, pressure is applied, and the components react to form a powerful bond. It is also suitable to premix the two components and apply the mixture to the surfaces to be joined. However, the high reactivity of the two components may only permit a short working time.

In assembling materials to be laminated, it is customary to subject them to bonding pressure in a suitable press, which can be operated at ambient temperatures, or heated to the desired temperature, e.g., to as high as 300-350F. The amount of pressure can be varied, but generally the pressures used in the art are suitable, e.g., pressures of the order of -200 psi. Pressure generally is employed to secure a good bond through intimate contact of surfaces.

The components of the adhesives of the present invention react readily at ambient temperature, e.g. from about 68F to about F, so the application of heat is not required. Elevated temperatures promote more rapid setting, however, and can be used after assembly of the article when high-speed reactivity is desired. Temperatures generally in the range of from about 1 10F to about 350F are suitable.

The above invention can be better understood by reference to the following examples. However, these examples are only for the purpose of illustration and it is not intended that the invention be limited thereby.

EXAMPLE l An alkaline aqueous dispersion of protein was prepared by mixing 50 g of casein (80 mesh, Argentine lactic grade) with 100 ml of water and g of 50% sodium hydroxide solution. The casein solution thereby obtained was a typically fluid, tacky material. The solution was divided into2 portions. To one portion 5 percent by weight of oxazolidine E was added, and to the other 5 percent of T. With E, gelation of the protein occurred in about 5 minutes, and with T gelation occurred in about minutes. When a freshly mixed sample of the casein solution with 5 percent T was heated, gelation occurred promptly when the temperature reached about l40F.

EXAMPLE 2 This experiment was performed to demonstrate the reactivity between the oxazolidine ,T and soybean from commercial soybean protein, 400 g, and dispersed in 1600 g of water with SOpercentsodium hydroxide solution, 57 g. The soybean protein dispersion was then mixed with 1 percent by weight of oxazolidine T'to give a proportion of protein to T of about 20:1 and applied to the veneer layers at about 50 lbs./ 1,000 sq.

'ft. of single glue line.

EXAMPLE 3 A dispersion was prepared by mixing 100 g of a commercial soybean flour with 400 g of water (70F) and 11.4 g sodium hydroxide. Five g oxazolidine T" per 100 g of-the wet adhesive mix was added to provide a ratio of about 4:1 of protein to T, and the fluid mixture was heated in a water bath. A firm gel developed when the adhesive temperature reached between about 168F and 175F. In the absence of T," no gel developed on heating to 175F or after holding at 212F, for extended periods.

The above experiment was repeated except that 10 percent sodium silicate (wet glue basis) was mixed with the soybean protein. Then Ipercent of T dissolved in water was added to the mixture to provide a ratio of about 20:1. A firm gel was produced when the mixture soybean flour and 400 g water was mixed and to g of this wet mix, 1 g of T was added to provide a ratio of about 20:1 of oti to .T. This fluid mi produced a gel at l7 -l 5 F. When the concentratio:

of T" was increased to 5 g, (i.e.,4:l of protein to T" a gel was obtained at F.

EXAMPLE 4 The following experiment was conducted with a soybean flour dispersion prepared as follows:

soybean flour 400 g water 1680 g NaOH (50% solution) 122 g Total 2202 g The above colloidal mixture had a ratio of 15 g of NaOI-I solid per 100 g of soybean flour.

An aliquot of 100 g of the solution was mixed with 5 ml of oxazolidine E (5.35 g), to give a ratio of EXAMPLE 5 An alkaline soybean dispersion was prepared in accordance with Example 4 except that only 55 g of 50 percent aqueous sodium hydroxide solution was employed, giving a final concentration of 6.7 g NaOI-I per 100 g of soybean flour.

To a 100 g aliquot of the above aqueous mixture was added- 5 g of oxazolidine T to give a ratio of 3.721. One sample of this solution gelled at 150F and another gelled in 1% hours at room temperature.

A typical corrugated paper laminate was prepared using the above mixture containing T at a press time of 20 seconds at 300F. The resulting laminate exhibited 100 percent bond even after a 6-hour soak in water.

We claim:

1. In a process for joining two surfaces of at least two cellulosic articles by applying an alkaline casein or soybean protein solution to one surface and a second component capable of forming an adhesive with said protein, the improvement consisting of applying as said second component an oxazolidine of the group represented by the formula 0 N o c o H1 H2 wherein R is ethyl or hydroxymethyl.

I I i t v zg ggg I UNITED STATES PATENT OFFICE I CERTIFICATE OF CORRECTION Patent NO. 3, Dated December 19 Invenwfls) John T. Stephan and A. J. Golick It is certified that errbr appears in the above- I identified patent and that said Letters Patent are hereby corrected as shbwn below:

Column 2, line 12 "945" Should be l945- Signed and sealed this 17th dey of April 1973.

(SEAL) Attest:

EDWARD M. FLETCHER,J-R. v ROBERT GOTTSCHALK Commissioner-of Patents Attesti ng Officer 

